The cost of overlapping of agricultural implements is well understood. When applying agricultural products such as seed, fertilizer, and chemicals the overlapped portions of the field receive twice as much of the products as is desired. The cost of the agricultural products thus wasted can be significant, and as well there are significant undesired effects of double seed and fertilizer application, such as the tendency of crop in overlapped areas to fall down or lodge.
As the width of field implements increases, overlaps become an increasing concern as well. For example where a narrow strip of ground perhaps 10 feet wide remains to be done at the end of a field operation, and where the machine being used is 60 feet wide, if no sectional controls are provided then to complete the field a strip 50 feet wide will be overlapped the whole length of the field, whereas if the machine is only 30 feet wide the overlapped strip is only 20 feet wide.
Sectional shutoff control for portions of implement that apply agricultural products such as seed, fertilizer, and chemicals has therefore become more desirable. These controls allow for application of agricultural products do be stopped at selected portions of the implement. For example a 60 foot wide air seeder might have four sections that can be turned off selectively, allowing the air seeder to apply seed and fertilizer over 60 feet, 45 feet, 30 feet, or 15 feet. Thus it can be seen that overlap can be greatly reduced.
Sectional shutoff control has been common for some time on agricultural field sprayers. On this equipment when the sprayer passes over an area that has already been sprayed, the overlapping portion of the sprayer can be turned off by the operator.
With the advent of external guidance systems using the Global Positioning System (GPS) or in some cases towers broadcasting location signals, such sectional shutoff control can be accomplished automatically.
Such external guidance systems have been developed to guide an implement along a desired path. Typically in agricultural field operations the implement will be towed by a tractor or like vehicle and the object is to cover the entire field by passing back and forth over the field with the edge of the implement located just at the edge of the last pass such that no part of the field is missed, and yet overlap is kept to a minimum. The implement may also be mounted directly on the vehicle instead of being towed, so as to be moved along the field with the vehicle. For example in self-propelled sprayers the implement comprises spray booms extending laterally from a vehicle carrying a spray tank, pump, and like operational equipment for the implement. Similarly, tillage and seeding implements can be mounted on a tractor by a three point hitch arrangement, as well as being towed by the tractor.
External guidance systems include receivers mounted on the vehicle to receive location information from global positioning satellites or from radio transmitter towers. The system is programmed to track the location of the vehicle over time, and using this location data, a microprocessor provides a steering guide for the vehicle.
The width of the implement being used is entered into the microprocessor and the external guidance system continuously determines the location of the vehicle and the microprocessor tracks and stores the path the vehicle takes as it passes across the field. The microprocessor can thus determine a desired second path adjacent to a first pass by moving the second path over one implement width from the first pass. As the vehicle moves along the field to create the second path, the microprocessor indicates to the vehicle operator the actual location of the vehicle compared to the desired location that is on the second path. In one common system, a light bar is used. A green light in the center of the bar indicates that the vehicle is at the correct location, while yellow lights to each side indicate a variance to the left or right, and the operator steers the vehicle accordingly. Other indicators are also known.
Automatic steering systems have now been developed whereby the microprocessor is used to actually steer the vehicle as opposed to simply indicating to the operator which direction he should steer. Typically the vehicle will be steered by a steering actuator, commonly a hydraulic steering cylinder, that is extended and retracted to steer the vehicle in response to signals from the steering wheel of the vehicle. In an auto-steering system, the microprocessor sends steering signals to the steering actuator. Using the above example of the light bar indicator, when the light is green, the microprocessor steering signal would maintain the actuator in its current position. When a yellow light indicates a variance from the desired location that is on the desired path, the microprocessor steering signal extends or retracts the steering actuator to steer the vehicle toward the desired path. When the guidance system senses that the vehicle is at a location that is on the desired path, the microprocessor steering signal would again maintain the actuator in its current position.
When using an external guidance system, an operator will commonly make about two passes around the field with the implement to establish the field boundaries in the microprocessor, and to provide a turning area, and then make passes back and forth across the field starting at one straight edge of the field and working across the field until the field is completed. Some areas of overlap are unavoidable such as when the implement meets the end of the field at an angle other than perpendicular, but these areas are relatively small and of no great concern.
The main concern with overlap is when a strip of field possibly a mile long remains to be seeded that is substantially narrower than the implement being used. For example the strip may be 10-15 feet across and the implement 60 feet wide, leading to a significant area of overlap.
Product sectional shutoff controls that are controlled by external guidance systems such as GPS are available for seeding implements. This technology has evolved from spraying equipment where sections of a spray boom are turned off to avoid overlap, and similarly with seeding implement when the seeder reaches the last narrow pass, the external guidance system gauges where the field has been seeded and where the unseeded strip is located in relation to the implement and automatically turns on seed and fertilizer distribution to the implement sections that are required to cover the unseeded strip, and turns off seed and fertilizer distribution to the sections that are overlapping the already seeded portions of the field.
Unlike sprayers however, seeding implements include furrow openers that engage the ground. The furrow openers that travel over the already seeded areas thus disrupt the seed and fertilizer that has been placed at carefully selected locations with respect to each other, and at a desired depth, and that has typically been packed to ensure good seed to soil contact and promote quick germination. Thus where the 60 foot wide implement is seeding a 10 foot wide strip while deposition of seed and fertilizer is halted on the overlap areas, the furrow openers disrupt the seed and fertilizer in a strip 50 feet wide the length of the field, reducing optimum conditions for seed germination and productivity.
To address this problem, work is being done to develop implements where the product sectional control signals that control distribution of agricultural product to the separate sections of the implement also lift the furrow openers in those sections where distribution is stopped. Thus the furrow openers that are traveling over already seeded areas are raised above the ground and do not disrupt the seed and fertilizer already placed and packed. Such developments introduce considerable added expense and complexity to the seeding implement, and contribute to added maintenance and downtime due to equipment failure. Further, lifting a large number of openers on one side of a drill causes uneven draft from right to left and causes the implement to skew.